1. Field of the Invention
The present invention relates to a volume-dependent accounting system and method for managing a session between a client and server and performing an accounting process at a request of a user in a service through connectionless communications such as a World Wide Web (WWW).
2. Description of the Related Art
Recently, various networks connected through the Internet and the server computers in the networks realize information groups referred to as WWW. In a WWW, a service-requesting client computer is provided with software referred to as a browser for communicating with the server.
When the browser requests the server to provide a service such as retrieval of data from a database in such a WWW, there is the problem that a session should be properly managed. A session refers to the communication established between the users recognized when the communication is set.
Normally, since the hyper text transfer protocol (HTTP) used by the browser is a connectionless protocol, the session is set when the browser requests a page and terminates when the server transmits the page. Therefore, when the client accesses another screen, another session is set with the relation to the previous communication unsaved.
As a result, various problems arise when the WWW is used with a database. Normally, a database server can consecutively perform a plurality of processes once a client logs in. However, when data is to be retrieved using a combination of a WWW and a database, a process cannot be successfully performed if the communications between the client and server cannot be completed with one question and answer. For example, if a process continues from the previous page as in a converging retrieval, it is recognized as another session.
Therefore, when the sessions are managed in such a combinational system, resident combined software can be incorporated in addition to a non-resident common gateway interface (CGI) program to recognize a session established covering a plurality of screens. A session continues if the combined software confirms a session identifier transmitted from the browser.
However, the above described WWW has the following problem.
Incorporating a combined software into a server to manage a session covering a plurality of screens does not guarantee the next access by the browser of the session. Therefore, there arises the problem that the combined software indefinitely repeats checking of the identifier. Thus, the resident combined software should be developed in consideration of various conditions.
When a service for a client includes information using a WWW server, the server should correctly charge the user for a service in addition to the problem of the session management. The accounting system can normally be a fixed-amount system or a volume-dependent system.
In the fixed-amount system, a fixed fee is charged to a user's account for each period as long as a user to be charged can be identified. Therefore, this system is relatively easy to realize. On the other hand, the volume-dependent system has quite a few problems.
A basic volume-dependent system is based on the time of access obtained from the access log of the server. However, communications are often disconnected on the network, and the user may not be able to obtain the transmitted contents. Therefore, correctly recording an "access" into the log does not indicate that the requested information has been successfully transmitted to the user.
The data transmission may be either intentionally interrupted by the user or accidentally interrupted through a problem in the network. The former case is normally referred to as an `interrupt`.
The user's intentional interrupt indicates the state in which the transmission of data is suspended by the user by, for example, clicking a mouse button, that is, a pointing device such as a mouse, on the stop button (read stop button) on the display screen of the browser. A problem in the network indicates a state in which data have been lost due to, for example, network overload.
Thus, in the volume-dependent accounting system, it is required that a user is not charged for a suspension of data transmission and that the accounting timing should be clearly defined to provide a user-friendly man-machine interface (MMI). At present, one user identifier is often shared among a plurality of users, and an appropriate mechanism is required to charge a user for a service after correctly recognizing who, of the users having the same user identifier, has accessed data.